With the transition from film cameras to digital cameras including image pickup devices in recent years, cameras have become capable of not only shooting still images but also shooting simple moving images, just as video cameras can. Some of so-called single-lens reflex cameras with interchangeable lenses employ a movie shooting mode, in addition to a still image shooting mode. Single-lens reflex cameras described herein mean camera bodies in which subjects are observed through observation optical systems including so-called reflex mirrors, and camera bodies in which images are displayed on liquid crystal display monitors through which the images are observed.
When the still image shooting mode is selected, the camera body performs an operation of shooting a still image. When the movie shooting mode is selected, the camera body performs a continuous shooting operation. In the movie shooting mode, unlike in the still image shooting mode, actuators included in the interchangeable lens that are provided for focusing and aperture moving operations also need to operate continuously. To control driving of such actuators, it is important that the state of the interchangeable lens, including the focus and aperture states, are frequently monitored.
Monitoring of the state of the interchangeable lens and drive control of the actuators are realized by communication between the interchangeable lens and the camera body. However, known communication methods, in which only still image shooting is considered and therefore the speed of communication is low, are not suitable for continuous shooting.
To solve such a problem, Patent Citation 1 discloses a technique in which, if an accessory that has been mounted on a camera body is found to employ a recent communication method, the clock rate of communication is increased.
Patent Citation 1: Japanese Patent Laid-Open No. 2001-350190